U.S. Pat. No. 5,722,474 (Raybon et al) entitled “Method and apparatus for cutting a cant into boards” and U.S. Pat. Nos. 5,761,979 and 5,870,936 (McGehee) (Canadian equivalent 2,198,662) both entitled “Edge trimming and board ripping apparatus and method” relate to the processing of wood cants of irregular shape. The objective is to facilitate high speed sawing of wood cants of irregular shape into dimensionally similar portions of sawn lumber for the purpose of maximizing solid lumber recovery.
The preferred method described in McGehee involves the steps of: 1) scanning a wood cant to determine a cutting pattern; 2) directing the wood cant through a saw assembly consisting of saw blades mounted on and rotated by a rotating arbor; 3) adjusting in unison the skew angle of the saw blade axis of each of the saw blades relative to the arbor axis, with such adjustments being carried out while the saw blades are rotated by the arbor in order to cut the wood cant according to the cutting pattern determined by scanning step. As the skew angle of the saw blades is adjusted, the lateral position of the saw blades in relation to a centerline of the blade supports is altered. The operation is computer controlled with this lateral offset of the saw blades accommodated in the programming of the computer.
A limiting factor in applying the teachings of the McGehee method is in the saw blade steering apparatus used to adjust in unison the skew angle of the saw blades. Existing apparatus are expensive to manufacture and maintain, due to their complexity.